Rosco Manufacturing Bloodline AR-15 .300 AAC Blackout Threaded AR Barrel 7.5in Heavy Pistol Length 1-5 Twist 5/8x24 Nitride Black. 50" Nitride 4 - This Rosco 7.5" 300 Blackout Bloodline Barrel was designed for SBR and Pistol use in conjunction with suppressors. This is the shortest that we will go to allow the flexibility of a shorter Personal Defense Weapon (PDW) without sacrificing performance or ballistics. Specifications for Rosco Manufacturing Bloodline AR-15 .300 AAC Blackout Threaded AR Barrel: Manufacturer: Rosco Manufacturing Color: Black Finish: Nitride Caliber: .300 AAC Blackout Barrel Length: 7.5 in Barrel Profile: Heavy Gas System Length: Pistol Length Gas Block Journal Size-Diameter: .750 in Barrel Twist Rate: 1-5 Barrel Material: 4150 CMV Steel Gun Make: AR Platform Gun Model: AR-15 Weight: 17.23 oz Gun Type: Rifle Firearms Threads Per Inch: 5/8x24 Length: 7.5 in Rosco Manufacturing BL-075-HB-300BLK-5-P Bloodline 300 Blackout 7.50" Nitride 4 Rosco Manufacturing BL-075-HB-300BLK-5-P: Bloodline AR-15 .300 AAC Blackout Threaded AR Barrel 7.5in Heavy Pistol Length 1-5 Twist 5/8x24 Nitride Black